Gnome-shell: Fix dark text in calendar event time

gnome-shell/_common.scss

@@ -976,6 +976,10 @@ StScrollBar {
       font-weight: bold;
     }
 
+    .events-button .event-time {
+      color: darken($fg_color, 4%);
+    }
+
     .world-clocks-grid {
       spacing-rows: 0.4em;
     }

gnome-shell/gnome-shell.css

@@ -889,6 +889,9 @@ StScrollBar {
   color: #5d5e60;
   font-weight: bold; }
 
+.events-button .event-time {
+  color: #8ca1a9; }
+
 .world-clocks-grid {
   spacing-rows: 0.4em; }